Mulligan, C. B., & Sala-i-Martin, X. (1999). Social security in theory and practice (II): Facts and political theories. National Bureau of Economic Research.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रMulligan, Casey B., और Xavier Sala-i-Martin. Social Security in Theory and Practice (II): Facts and Political Theories. Cambridge: National Bureau of Economic Research, 1999.
एमएलए (9वां संस्करण) प्रशस्ति पत्रMulligan, Casey B., और Xavier Sala-i-Martin. Social Security in Theory and Practice (II): Facts and Political Theories. National Bureau of Economic Research, 1999.
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